visualizing sound directivity via smartphone sensors
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S C O T T H . H A W L E Y D E P A R T M E N T O F C H E M I S T R Y & P H Y S I C S
B E L M O N T U N I V E R S I T Y , N A S H V I L L E T N U S A ( A C T I N G P R E S I D E N T , M U S I C C I T Y A S A C H A P T E R )
W I T H
R O B E R T E . M C L A I N , J R . O M E G A L A B S T U D I O S N A S H V I L L E T N U S A
Visualizing Sound Directivity via Smartphone Sensors
Session 1pED 5th Joint Meeting, Acoustical Society of America and
Acoustical Society of Japan
The App: Polar Pattern Plotter
Scott H. Hawley, Belmont University
FREE! 😀
Sample of ‘Apps’ Developed for Teaching AETs AET = Audio Engineering Technology, i.e. recording & live sound engineers
3D Audio Player
Reverb Time Measurement
Audio Session Documentation
Transistor Amplifier
“Cartoon Compressor”
Free Classroom Clickers
RLC Circuits
Simple Harmonic Motion
Rhyming Thesaurus (Songwriting)
Scott H. Hawley, Belmont University
The Story of PPP
� May 2016: Taught Gen-Ed Electro-acoustics class for Study Abroad, needed labs for us to do! ¡ Issues: student preparation, and “morale”
÷ Not too math- or Excel- intensive ÷ “Fast” and reliable ÷ Should be related to SA trip: speaker & mic
manufacturers ¡ Idea: automated data acquisition & visualization?
Scott H. Hawley, Belmont University
Story p. 2
� Manufacturers use “robot” systems for polar pattern measurement (Neumann HQ):
� Had idea for app: Mic input + Compass data -> Polar Pattern! Asked online (“Audio Educators Forum”), no such thing. …Yet!
� Wrote beta app in a couple days, students used my phone for lab
Scott H. Hawley, Belmont University
Story, p. 3
� Study Abroad bought Y-Adaptors for Phone Jack � Lab setup:
App queries compass to get rotation info Note: Compass near large permanent magnet!
Scott H. Hawley, Belmont University
Education Outcomes
� Students got graphs! � Students reported:
¡ Enthusiasm for teacher’s effort ¡ Appreciation for visual
representation ¡ Appreciation that it was directly
relevant to trip / mic-mfg
¡ Note: Dr. Yang-Hann Kim, in his Rossing Prize in Acoustics Education speech, identified visualization as *key* component for acoustics education.
Scott H. Hawley, Belmont University
Continued App Development
� Partnered with Rob McClain of OmegaLab Studio for measurement
� Offers “free field” / anechoic space
� Measured mics & multi-speaker setups
� Found gyroscope is more reliable than compass
� Identified need for more UI elem’s: meter, graph scale Scott H. Hawley, Belmont University
The App: Polar Pattern Plotter
Scott H. Hawley, Belmont University
Paper for The Physics Teacher
� The Physics Teacher journal, features a running “iPhysics” section on labs using smartphones
� Samples from submission by Hawley & McCain:
Scott H. Hawley, Belmont University
Student Results: Endfire Subwoofer Array
Endfire 40 HZ
Endfire 63 Hz
Endfire 80 Hz
M.Proctor, S.Dickenson, B. Hughes, J. Good, “Using Smartphones to Measure Subwoofer Array Patterns,” Student Project for PHY2010 – Physics for Audio Engineering, in progress (unpublished, 2016).
ArrayCalc: ArrayCalc:
Scott H. Hawley, Belmont University
Issues / Future Work
� Issue: Angular drift ¡ Gyroscope/Compass API (“DeviceMotion”) lacks accuracy, e.g.
shows 370o rotation when only 360o occurred (physically) ¡ Seems to be a known issue with such devices ¡ For now, added a tunable ‘drift correction’ multiplier (0.97).
÷ This version is not pushed to the App Store yet.
� Feature request: add a tunable filter, to ¡ Reject noise ¡ Allow for simultaneous experiments (at different frequencies)
� Some kind of “click” feature to reject room reflections?
Scott H. Hawley, Belmont University
Future Work 2
� Study Fraunhofer Diffraction (using accelerometer):
� Release as Open Source on github.com/drscotthawley � 3D Sound Visualization in VR, via HTC Vive Scott H. Hawley, Belmont University
Connections: Student trip to Japan in 2018?!
Scott H. Hawley, Belmont University
� In May 2016, did a dual-class Study Abroad program in Electro-Acoustics (Physics) and International Music Business (with an emphasis on Product Marketing) ¡ Brought students to Germany & Austria to visit Electro-
Acoustics research institutes (TU-Berlin, Fraunhofer IDMT, ARI in Vienna) and product manufacturers (Neumann, AKG)
¡ Personal connections established at AES made the trip great. � In 2018 we want to visit Japan! (Part of why I’m here) � Colleagues in Japan: Please come talk to me to
establish connections for planning a good trip! � Contact info: scott.hawley@belmont.edu
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